1. Field of the Invention
The present invention relates to an optical pickup and a disc drive apparatus. More minutely, the present invention relates to a technical field of an optical pickup including an objective lens driving apparatus in which a movable block is supported by a fixed block with a support spring put between them and the movable block is moved in three directions of a focusing direction, a tracking direction and a tilt direction, and a disc drive apparatus provided with the optical pickup.
2. Description of Related Art
There is a disc drive apparatus for performing the recording and the reproducing of an information signal into and from a disc-shaped recording medium such as an optical disc and a magneto-optical disc. Such a disc drive apparatus is provided with an optical pickup, which moves in a radial direction of the disc-shaped recording medium to radiate a laser beam to the disc-shaped recording medium.
The optical pickup is provided with an objective lens driving apparatus. A focusing adjustment is carried out by the objective lens driving apparatus moving an objective lens held by the movable block thereof in a focusing direction, which is the direction in which the movable block approaches to or withdraws from the recording surface of the disc-shaped recording medium. Also a tracking adjustment is carried out by the objective lens driving apparatus by moving the objective lens in a tracking direction, which is substantially a radial direction of the disc-shaped recording medium, and thereby the optical pickup condenses the spot of a laser beam to be radiated onto the disc-shaped recording medium through the objective lens to a recording track of the disc-shaped recording medium.
As described above, the optical pickup generally performs the focusing adjustment and the tracking adjustment by means of the objective lens driving apparatus. However, in recent years, for achieving improvement of the traceability of a spot of a laser beam to a recording track, an objective lens driving apparatus called a “three-axis actuator” has been developed. The three-axis actuator also enables the adjustment at the time of the occurrence of surface vibrations and the like of a rotating disc-shaped recording medium by enabling the movable block to tilt to the recording surface of the disc-shaped recording medium in addition to the two-axis direction adjustment of the focusing adjustment and the tracking adjustment.
Such objective lens driving apparatuses called the three-axis actuators, for example, include one which moves a movable block in three directions of a focusing direction, a tracking direction and a tilt direction by means of a plurality of coil bodies each made by unifying a focusing coil, a tracking coil and a tilt coil (see, for example, Patent Document 1).
Moreover, the objective lens driving apparatus called the three-axis actuators, for example, also include one which moves a movable block into a focusing direction and a tracking direction by means of a coil body made by unifying a focusing coil and a tracking coil, and which moves the movable block in a tilt direction by means of a plurality of tilt coils provided separately from the focusing coil and the tracking coil (see, for example, Patent Document 2).
[Patent Document 1] Japanese Patent Application Publication No. Hei 10-261233
[Patent Document 2] Japanese Patent Application Publication No. 2001-110075